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OCR for page 265
Issues in Risk Assessment
5
Conclusions
Risk assessment is defined as a general process for linking science to decision-making. Definitions and concepts for ecological risk assessment can be defined analogously with those provided for human health risk assessment in the NRC's 1983 report, Risk Assessment in the Federal Government: Managing the Process. The scope of ecological risk assessment, defined in this way, is not limited to technical analyses supporting day-to-day regulatory decisions. Ecological risk assessment can also contribute to strategic planning within and between federal agencies and to clarifying the ongoing public debate concerning national and international environmental priorities.
The four-part framework for health risk assessment (hazard identification, dose-response assessment, exposure assessment, risk characterization) described in the 1983 report insufficiently characterizes the interaction between science and management in risk assessment. Management considerations (e.g., regulatory constraints on the scope or time available for an assessment for legally prescribed definitions of acceptable or unacceptable risks) shape the hazard identification step. Communication of risks in terms relevant to decision-making is a critical aspect of risk characterization that was largely unexplored in the 1983 report. (This topic was explored in a subsequent NRC report, Improving Risk Communication (NRC, 1989)). Although the deficiencies were initially identified by the committee with respect to ecological risk assessment, the committee believes they are relevant to human health risk assessment as well.
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Issues in Risk Assessment
If the definitions used in the 1983 report are expanded then, with minor changes in terminology, a single framework can accommodate both human health and ecological risks. Hazard identification should be expanded to include identification of policy considerations or regulatory mandates that influence the scope and objectives of an assessment. Risk characterization should be expanded to provide explicit discussion of uncertainty, facilitate expression of risks and management-relevant terms, and emphasize the importance of communication between scientists and managers. Prospects for integration of human and ecological concerns into comprehensive environmental policies that are protective of both will be enhanced if the assessments employ a common framework and terminology.
Several scientific problems are common to all types of ecological risk assessments. Most of them are now subjects of active scientific research: extrapolation across scales of time, space, and ecological organization; quantification of uncertainty; validation of predictive tools; and valuation, especially quantification, of nonuse values.
Technical guidance is needed on the scientific content of ecological risk assessments. In-depth analysis of the scientific issues involved in specific applications of ecological risk assessment is beyond the charge of this committee. Additional expert committees drawn from the academic, public, and private sectors are needed to address these issues. The workshop summary (Appendix H) contains many specific examples of topics for which guidance is needed; the NRC's report Ecological Knowledge and Environmental Problem-Solving (NRC, 1986) provides a useful model for synthesis and presentation of the science relevant to improving ecological risk assessments.
